Transformer



March 14, 1961 c s, ASHMAN r 2,975,358

TRANSFORMER Filed Sept. 8, 1958 COMPENSATING LOAD FIG.2

FIG.1

INVENTORS C. S- Ashmcm B.H.L.

James AGENT United States Patent TRANSFORMER Charles Stanley Ashman, Epsom, Brian Harry Laurence James, Reigate, and Michael Terence Stockford, South Croydon, England, assignors to North American Philips Company, Inc., New York, N.Y.

Filed Sept. 8, 1958, Ser. No. 759,604

Claims. (Cl. 323-51) The present invention relates to transformers and arose from the problem necessitating the feeding of a certain pulse voltage to one part of an electrical circuit and a second lower pulse voltage capable of being varied but adjustable to any desired fraction of the certain pulse voltage to another part of the electrical circuit.

According to the present invention, a transformer comprises a primary core and two secondary cores, a winding associated with each core, one secondary core being an output core and the other secondary core being a loadcompensating core, means securing the two secondary coils relative to one another and means for moving the primary core relative to the secondary cores whereby on movement of the primary core relative to the secondary cores the change of load due to the movement of the primary core relative to the output secondary core is compensated.

The compensation need not be exact for all positions of the primary core relative to the secondary bore but for any given case should be such that the loading constancy and hence the nature of the output of the transformer, for example, the pulse shape, has a desired similarity to that of the input of the transformer. The transformer may be used for pulsed or continuous wave inputs within the limits of its power dissipation, losses and frequency characteristics.

The ends of the secondary cores and the primary cores may be in contact to provide the magnetic transformer coupling, the ends of the cores being cylindrically shaped with equal radii of curvature, the shaping in the case of primary core being in opposite sense to that of the secondary cores and the arrangement being such that the three centre of curvature lines are coincident. It has been found convenient if the secondary cores are at an angle of 55 to 65, specifically about 60, to one another in planes perpendicular to the common centre of curvature line of the cylinders. The three cores may be 0- cores and both limbs of each core cylindrically shaped.

One embodiment of a transformer according to the invention will now be described by way of example with reference to the accompanying diagrammatic drawing in which:

Figure 1 is a plan view and Figure 2 is a side view taken from the left of Figure 1.

Referring now to the drawing, a transformer comprises a primary core 1, an output secondary core 2 and a loadcompensating secondary core 3. e

Each core is a C-core, is substantially identical and is made from .002 inch thick laminations.

The ends of each core are cylindrically shaped with equal radii of curvature, the shaping in the case of the core 1 being convex and in opposite sense to that in the case of the cores 2 and 3 which is concave.

The cores 1, 2 and 3 are arranged with the three centre of curvature lines coincident at 4 and with the primary core 1 in contact over its entire cylindrical surfaces with those of the secondary cores 2 and 3. The cores 2 and 3 are arranged at an angle A: 60 with one another (Figure 1) in planes perpendicular to the common centre of curvature line 4 of the cylinders.

The figures are substantially to scale and the dimension B is about 3 cms.

The transformer is designed to give a pulse output varying between 0 and 8 kv. at a current of 10 amps. from a pulse input of 8 kv. and 10 amps. with a pulse recurrence frequency of about LOGO/sec. and a pulse width of l to 2 sec.

Each core 1, 2 and 3 has a winding 10, 11, and 12, re-

spectively, of 50 turns of 24 S.W.G. insulated copper wire,-

25 turns on each limb in series wound on an insulating former and insulated with insulating paper.

sistance equal to that of a load 7 or utilization means to be connected across the winding of core 2. The windings, formers and other insulation are provided in any convenient known manner and are not shown.

The cores 1, 2 and 3 are secured to a frame member, not shown, the cores 2 and 3 being held in a fixed relationship with respect to the frame member and the core 1 being secured to the frame member so as to be rotatable about the line 4.

The position of the core 1 relative to the cores 2 and 3 can be varied from maximum coupling between cores 1 and 2 to minimum coupling between cores 1 and 2, the coupling between cores 1 and 3 increasing as that between cores 1 and 2 decreases. The total loading provided by cores 2 and 3 is equal at the positions of maximum and minimum coupling between cores '1 and 2 and is slightly lower at intermediate positions of the core 1 so that the source 8 feeding into the winding on core 1 is substantially uniformly loaded and the output waveform bears a substantially constant similarity to that of the inputwaveform.

The cylindrical surfaces of the cores 1, 2 and 3 are smooth and it is found that in this case the discontinuities between the cores 1 and 2 and 1 and 3 do not have an undesired effect.

What is claimed is:

1. A transformer providing variable output but substantially uniform source loading, comprising a primary magnetic core having end portions, first and second secondary magnetic cores having side-abutting end portions extending in a given direction forming a continuous surface opposed to and contacting the primary core end portions, separate windings coupled to each of the magnetic cores, and means for moving in said given direction and relatively to one another the primary core end portions and the said continuous surface formed by the secondary core end portions so that the relative magnetic coupling of the primary core to the first secondary core may be varied but the total magnetic coupling of the primary core to both secondary cores remains essentially the same.

2. A transformer as set forth in claim 1 wherein all of the core end portions are cylindrical with the same radius of curvature, but the cylindrical shape of the primary core end portions is in the opposite sense to that of the secondary core end portions.

3. A transformer as set forth in claim 2 wherein the cylindrical end portions have a common center of curvature line, and the first and second secondary cores are at an angle between 55 and 65 to one another in a plane perpendicular to the said common center of a curvature line.

4. A transformer providing variable output but substantially uniform source loading, comprising a C-shaped primary magnetic core having end portions, first and second C-shaped magnetic cores having side-abutting end portions extending in a given direction and forming a con- Patented Mar. 14, 1961 The wind-- ing on the core 3 is loaded by a resistor 6 having a re tinuous surface opposed to and contacting the primary core end portions, separate windings coupled to each of the magnetic cores, and means for moving in said given direction the primary core end portions relative to the said continuous surface formed by the secondary core end portions so that the relative magnetic coupling of the primary core to the first secondary core may be varied but the total magnetic coupling of the primary core to both second cores remains essentially the same.

5. A transformer system providing variable output to a utilization device but substantially uniform source loading, comprising a primary magnetic core having end portions, first and second secondary magnetic cores having closely adjacent end portions forming a substantially continuous surface opposed to the primary core end. portions, separate windings on each of the magnetic cores, means coupling the winding on .the primary: core tothe source, means coupling the winding on thefirst secondary core to the utilization device, means coupling the winding on the second secondary core to a compensating artificial load, and means for moving relatively to one another the primary core end portions and the said substantially continuous surface formed by the secondary core end portions so that the relative magnetic coupling of the primary core to the first secondary core may be varied to vary the transformer output but'the total magnetic coupling of the primary core to both secondary cores remains essentially the same affording substantially constant loading of the source.

References Cited in the file of this patent UNITED STATES PATENTS 

